Various and Sundry

I don’t know if I ever mentioned this, but quite a while ago I replaced the “latexrender” TeX plugin being used here by a mathjax one. As I find time, I’m now going back and editing old posts to get rid of latexrender tags and make the equations more mathjax friendly. As far as comments are concerned, you can add TeX content by using standard math delimiters \$, or \$\$ for displayed math. If you want to comment about US dollars, put a backslash before your dollar signs to avoid the interpretation as TeX.

One reason I hadn’t advertised this much is that I know it’s hard to get TeX right the first time, so people’s comments with TeX would be likely to often not work properly. I’ve added a plugin that lets you edit your comment for 5 minutes after you write it. This should be useful for typos, as well as for fixing TeX problems (note that you need to refresh the page to get the math to display).

For a philosopher’s take on evaluating string theory, see this talk by James Ladyman, on Cosmic Dreams. Material on string theory is near the end, and just makes the obvious point that having no experimental evidence for the theory is a huge problem, no matter what efforts are made to change the usual way scientific theories are evaluated.

A hot topic these days in the math community is the conjecture that local Langlands can be understood as geometric Langlands for the Fargues-Fontaine curve. My attempts to learn about this so far haven’t had a lot of success, but I now have new-found hope. At Harvard there’s a seminar going on this semester on the topic, and it has a website which so far features explanations of some of the mathematics involved from Jacob Lurie and Dennis Gaitsgory. In London, the London Number Theory Seminar also has a study group devoted to this topic (website here, although seems to have disappeared for the moment).

Today came an announcement that a Virgo detector together with two LIGO detectors recorded a black hole collision:https://www.nsf.gov/news/news_summ.jsp?cntn_id=243239
“This discovery, announced today, is the first observation of gravitational waves by three different detectors…”

What I just heard is that there are rumors of another event, not two black holes, but a black hole and a neutron star, and that for that event there was EM confirmation. Supposedly observed a few days after this one. No comment as yet about it from either LIGO or VIRGO.

No EM counterpart for this event – from the NSF announcement:
“Being able to identify a smaller search region is important, because many compact object mergers — for example those involving neutron stars — are expected to produce broadband electromagnetic emissions in addition to gravitational waves,” says Georgia Tech’s Laura Cadonati, deputy spokesperson for the LIGO Scientific Collaboration. “This precision pointing information enabled 25 partner facilities to perform follow-up observations based on the LIGO-Virgo detection, but NO counterpart was identified — as expected for black holes.”

The characterization of LQP2 as a website that collects information about “relativistic quantum theory” may be overly broad. As any community website, it’s content is dictated by the members of that community. But, at least historically, the focus of that community has been more narrowly the study of Algebraic Quantum Field Theory (AQFT), including also the study of QFT on Curved Spacetimes and sometimes even Non-Commutative Spacetimes using the methods/framework of AQFT. The name Local Quantum Physics actually reflects the title of the well known monograph by Rudolf Haag on this topic.

To follow up on Jeff M, I have a former student whom I dare not identify who might be on the LIGO team. He or she tells me, “You didn’t hear it from me, but the best is yet to come.” No more specific than that, but I think more and better are coming soon. Great timing! It’s gotta be either the whole LIGO team or Thorne and Weiss for this year’s Nobel. Nice article in the NYT by Dennis Overbye.

Igor, on the other hand, as we have discussed, the local quantum observables of any perturbative relativistic QFT do organize into a causally local net, and so all traditional perturbative relativistic QFT is, and secretly has been all along, local QFT in the sense of the Haag-Kastler axioms. In fact the Haag-Kastler axioms (for perturbative formal power series algebras of observables) may be *derived* this way from standard relativistic QFT. (I have written out the proof in full detail here, since it is curiously non-evident from the literature as you know. Thanks again for the hints that you had provided!) Therefore it sort of makes sense and possibly is about time to conflate “local quantum physics” in the community-specific sense with traditional relativistic QFT.

Sabine Hossenfelder has a nice article in Forbes “https://www.forbes.com/sites/startswithabang/2017/09/28/is-the-inflationary-universe-a-scientific-theory-not-anymore/#216075e0b45e” about inflation and if it’s science or not.